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Arterial spin labeling for acute stroke: practical considerations
1Department of Radiology, Stanford University, Stanford, CA, 94305-5488, USA, gregz@stanford.edu.
Abstract:
Arterial spin labeling (ASL) is a non-contrast method of measuring cerebral perfusion with MRI. It has several advantages over traditional contrast-based perfusion-weighted imaging, including non-invasiveness, more straightforward cerebral blood flow (CBF) quantification, and repeatability. However, because of its lower signal-to-noise ratio (SNR) per unit time and its high sensitivity to arterial transit delays, it has not been used frequently in acute stroke, where arterial delays and time-efficiency are of the essence. This is beginning to change, driven by higher SNR implementations of ASL and the increasing use of 3T scanners. Furthermore, velocity-selective ASL sequences that are largely insensitive to arrival times are beginning to be applied to patients with cerebrovascular disease and promise the ability to quantify CBF even in regions supplied by late-arriving collateral flow. Despite these advances, many practical issues must be addressed to optimize ASL for its use in acute stroke studies. These include optimizing the trade-off between time, SNR, imaging resolution, and sensitivity to slow flow. Rapid and robust post-processing of image data must be made routine, such that CBF maps are available in real time so that they can be considered when making treatment decisions. Lastly, automated software needs to be developed in order to delineate hypoperfused tissue volumes, which is challenging due to the inherent differences between gray and white matter CBF. Attention to these details is critical to translate this promising research tool into mainstream clinical trials and practice in acute stroke.
Insights
Arterial spin labeling (ASL) offers a non-contrast MRI method for measuring cerebral blood flow (CBF). Advances are making ASL more suitable for acute stroke imaging, but practical challenges remain for clinical use.
Area of Science:
- Medical Imaging
- Neuroscience
- Radiology
Background:
- Arterial spin labeling (ASL) is a non-contrast MRI technique for cerebral perfusion measurement.
- ASL offers advantages like non-invasiveness and straightforward cerebral blood flow (CBF) quantification.
- Traditional ASL has limitations in acute stroke due to low signal-to-noise ratio (SNR) and sensitivity to arterial transit delays.
Purpose of the Study:
- To review the evolving role and challenges of ASL in acute stroke imaging.
- To highlight recent advancements improving ASL's applicability in time-sensitive stroke scenarios.
- To identify key areas for development to facilitate ASL's clinical adoption in acute stroke.
Main Methods:
- Review of current ASL techniques and their modifications for improved SNR and reduced sensitivity to transit delays.
- Discussion of advancements in 3T MRI scanners and velocity-selective ASL sequences.
- Analysis of practical considerations for optimizing ASL in acute stroke research and clinical practice.
Main Results:
- Higher SNR ASL implementations and 3T scanners are increasing ASL's utility in acute stroke.
- Velocity-selective ASL shows promise for quantifying CBF in areas with delayed arterial arrival.
- Significant practical issues persist, including optimizing the time-SNR-resolution trade-off and sensitivity to slow flow.
Conclusions:
- ASL is becoming more viable for acute stroke imaging due to technological advancements.
- Further development is needed in optimizing ASL sequences, post-processing, and automated analysis for clinical integration.
- Addressing these challenges is crucial for translating ASL into routine clinical trials and practice for acute stroke management.
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